Simple parameter extraction of an IEGM can be a very useful tool in a variety of diagnostic features. Many algorithms in implantable or external medical devices are being or have been developed for diagnosing various conditions based on information extracted from the IEGM and various segments within a cardiac cycle. Many of these algorithms, such as ischemia detection, electrolyte imbalance, hypo- and hyper-glycemia, etc., are based on parameters extracted from the repolarization segment (the T-wave) of the IEGM. Because of the sensitivity of the T-wave to changes in O2, electrolytes, glucose, etc., such algorithms generally have a high sensitivity but lack good specificity. It would be beneficial if the specificity of such algorithms can be increased. More generally, it would be beneficial to increases the specificity of diagnostics based at least in part on measures of T-wave metrics of an IEGM.